At present, display technologies fall into 5 main types: LCD, plasma, CRT, OLED/LED and projection. These technologies cab be further categorized as follows:
1. Shuttered technology, such as LCD and projection, which allows light to pass in predefined parts of the screen to form the required image.
2. Emissive technology, such as plasma, CRT and OLED/LED that emits light at predefined positions on the screen to render the required image.
Shuttered technologies suffer from poor efficiency, because the light provided by a backlight is partially blocked. Neither technology performs well under bright lighting conditions. Transreflective LCD technologies, which reflect bright illumination, suffer from narrow viewing angles.
For touch-sensitive application, a tech-sensitive layer may be added to the display panel to enable user input using fingers or styli. For tactile applications, a tactile layer may be added that gives a textured or 3D representation.
All of the aforementioned technologies share similar drawbacks for touch-sensitive or tactile applications, in that an additional layer must be added directly over the visual display, therefore, degrading the light output, clarity and contrast of the display panel. Moreover, the additional layer and associated components add to the cost of the display.
Additionally, some touch-sensitive technologies based on row and column sensing in a matrix are only able to detect a single touch at any one time. Other touch-sensitive technologies have poor spatial resolution.